The USGA originally established COR testing to define the driver distance restrictions... Which stood for Coefficient of Restitution. The test essentially measured the energy lost at impact by striking an un-shafted driver head with a moving golf ball and then measuring both the incoming and rebound velocities.

These velocities and respected energies created a ratio (whose maximum legal value was 0.83). This COR ratio indicated how much energy was lost (or absorbed) in either the ball or head.

The USGA and R&A limit of 0.83 correlated to a 17% energy loss at impact, due to strain energy of the ball and head, heat, and noise.

USGA CT TESTING

The governing bodies later changed the COR test to a Characteristic Time (CT) test. The new test allowed drivers to be tested without damage and allowed them to be tested as complete clubs.

This helped permit testing "in the field" (such as on the PGA Tour) and eliminated the Variation of the ball from the equation.
Characteristic time measures how long the ball is on the clubface and reflects how much energy is transferred during impact. The USGA (and other governing bodies) have regulated a maximum 239 microseconds(µs) with a tolerance of 18 microseconds(µs). Any club that tests above 257 µs indicates that the head/face is too flexible and the club is deemed "non-conforming". Test values under 257 µs are acceptable.

Simplified: A higher CT time (µs) means less energy lost & more distance. For more information: USGA TESTING

OUR COMPETITIONS EFFORT TO CONFORM TO USGA LAWS

As a precaution against building non-conforming drivers, golf brands building conventional drivers must make certain allowances for the manufacturing related limitations inherent to their designs... Such as deviations in titanium thickness and welding variations. These precautions typically result in a driver below the USGA limit.

DNA's SOLUTION TO MAXIMIZE DISTANCE & STILL CONFORM TO USGA LAWS

DNA Golf has eliminated these issues with the patented "tunable" DNA Technology and can therefore deliver clubs that are virtually at the maximum USGA limit... delivering the highest face-flexibility (and thus distance) allowed by the ruling bodies of golf.